June 5, 2012 -- Waist size can predict your diabetes risk, even if you are not obese, according to a new study.
Diabetes experts have long used both body mass index (BMI), a measure of weight related to height, and waist size to predict risk.
Obese people, with a BMI of 30 or more, and non-obese individuals with large waists are considered at higher risk.
Now, the new research finds that waist size alone predicts risk of diabetes, especially in women.
Some overweight men and women with very large waists have the same risk of diabetes as obese people, says researcher Claudia Langenberg, MD, PhD, of the Institute of Metabolic Science, Addenbrooke's Hospital, in Cambridge, England. In BMI terminology, "overweight" is a step below "obese."
More doctors might consider using their tape measures, she tells WebMD.
"Our results now provide clear evidence that a simple measurement of waist circumference can identify overweight individuals (BMI 25-[29.9]) with a large waist, whose risk of future diabetes is equivalent to that of obese people," Langenberg tells WebMD.
A large waist is 35 inches or more in a woman and 40 inches or more in a man.
The findings are published in PLoS Medicine.
Waist Size, BMI, and Diabetes Risk
About 19 million Americans have diagnosed diabetes, according to the American Diabetes Association.
Most have type 2. The body does not make enough of the hormone insulin or the cells don't use it effectively.
Langenberg's team, the InterAct Consortium, re-evaluated data on more than 28,500 people.
Langenberg compared about 12,400 people with type 2 diabetes with about 16,100 people without.
They looked at their waist and BMI data.
Among the findings:
- Overweight women with a large waist (35-plus) and overweight men with a large waist (40-plus) had a 10-year incidence of diabetes similar to that of obese people.
- Higher waist size and higher BMI were each linked with higher diabetes risk.
- High waist size was a stronger risk factor for women than for men.
- Obese men with a large waist (40-plus) were 22 times more likely to develop diabetes than men with a low-normal BMI (18.5-22.4) and a smaller waist (less than 37 inches).
- Obese women with a large waist (35-plus) were nearly 32 times as likely to get diabetes than women of low-normal weight and a smaller waist (less than 31 inches).
"BMI measures overall adiposity and gives no information about fat distribution," Langenberg says.
Adiposity is a term used to represent fatness. Waist size reflects belly fat and fat around the internal organs, she says. That fat is strongly linked with type 2 diabetes.
Waist Size & Diabetes Risk: Perspective
The new research is ''basically fine-tuning what we have known for years," says Steven Edelman, MD, a diabetes expert and professor of medicine at the University of California, San Diego. He reviewed the findings.
While taking a patient's waist measurement ''wouldn't be a bad idea," doctors have many other ways to assess risk, he says.
They can take a good history, order lab tests, and simply eyeball the patient, he says.
It can be difficult to measure the waist exactly the same way each time, says James T. Lane, MD, the Harold Hamm chair in clinical diabetes research at the Harold Hamm Diabetes Center at the University of Oklahoma.
''It's helpful for measuring progress, but it's another statistic that should be used with caution by doctors because of the possibility for irregularity and inconsistency," Lane says.
"This further confirms that it is important to avoid carrying extra fat, particularly so around the abdominal region," Lane says. Fat hampers the body's ability to respond to insulin.
Edelman serves as a speaker, consultant, or advisory board member for Medtronic, Novo Nordisk, Lilly, Abbott, and other companies.
Lane has received grants or research support from Novo Nordisk, Boehringer Ingelheim, Merck, Pfizer, and other companies.